Saw chain guide bar



June 17, 1958 J. N. CUTRONE SAW CHAIN GUIDE BAR Filed NOV. 8, 1955 suenaouf;

United States i Patent O SAW CHAIN GUIDE BAR John N. Cutrone, Chicago,lll., assignor to Chain Tools,

This invention relates to improvements in guide bars for chain saws.

One of the common forms of guide bars for chain saws is a solid platearound which the endless chain moves and having sucient thickness sothat a peripheral groove may be provided in the edge of the guide bar toreceive the inner portions of the chain guide links, thus retaining thechain against lateral separation from the guide bar. Suitable laterallyextending shoulders or projections on opposite sides of the chainslidably engage the outer edge margin of this groove. In a currentlypopular type of chain such as is shown in the accompanying drawing theseb earing elements or shoulders are provided on the tie straps and on thecutter The shoulders on the tie straps and cutter links are in more orless continuous contact with the margins of the bar groove and howevergood the lubrication may be along the groove considerable friction doesoccur and power is required to overcome it. This friction is especiallynoticeable where the chain passes around the outer end of the guide bar.As a result of the friction not only is considerable power required toovercome it but wear on the guide bar groove in the course of timerenders it unfit for use, requiring the replacement of the guide bar bya new one.

The principal object of my invention is to reduce the friction in thatarea of the guide bar where the chain passes around its outermost orfree end, and this I accomplish by positioning a rotatable ring where itwill be encountered by the guide links of the chain supporting them withlittle or no friction as they pass around the outer end of the guide barwhile lifting the aforesaid shoulders away from sliding contact with thebar. In accomplishing the foregoing objective I provide a guide barassembly which is economical to manufacture, and at the same time sturdyand durable.

Other objects and advantages of the invention will be mentionedhereinafter or will become apparent from a perusal of the followingspeciication.

In the drawing:

Fig. 1 is a plan view below line 2--2 and a sectional view above line2-2 of the outer end of a guide bar made in accordance with thisinvention, showing mounted thereon a commercially used chain of the typeshown in U. S. Patent 2,508,784;

Fig. 2 is a sectional view on the line 2-2 of Fig. 1;

Fig. 3 is a sectional view on the line 3 3 of Fig. 1; and

Fig. 4 is a plan View, on a reduced scale, showing the bar and a chain.

Referring now to the drawing, the guide bar assembly comprises a pair ofouter plates 11 and 12 and an intermediate spacing plate 13 which, whenassembled ready for operation, will be firmly secured together in anyappropriate manner by riveting or, preferably, by spot welding. Whenviewed externally this assembly has the appearance illustrated in Fig.4, and may be provided with conventional means for attachment to a powerunit.

2,839,096 Patented June 17, 1958 ice It should be noted that theintermediate plate 13 has a curved recess 14 shaped and spaced from theouter end of the bar to partially embrace the stationary disk 15 and therotatable at annular ring 16.

In place of the disk 15 I might provide an annular ring instead of thesolid disk but the disk is preferable for a number of reasons relatingto economy of manufacture and assembly. This disk when welded againstthe plate 11, for example, provides an inner race against whichanti-friction bearing elementsl such as balls 17 may rotate, therotatable ring 16 constituting the outer margin of the raceway. Afterthe disk 15 has been welded to one of the plates 11 or 12 and therotatable ring 16 arranged concentrically thereabout, the balls 17 orroller bearings, if desired, will be placed between the disk and thering and, when the other plate is then welded against 'the disk and thering and, when the other plate is then welded against the disk 15, theanti-friction elements are prevented from escaping.

AThe plate 13 and disk 15 will be of the same thickness and just thickenough to afford a groove of desired width at the edges of the bar. Thering 16 will be slightly lows. The lateral margins 18 and 19 of theintermediate plate are located as shown, hence a recess or groove ofample depth is provided into which the chain guide links 21 may extend,while appropriate shoulders or bearing surfaces such as 20 on the chainride along the outer margins 22 and 23 respectively of the guide barplates 11 and 12. On a saw chain of the type indicated these bearingsurfaces are the shoulders provided on the tie straps such as 24 andsimilarly placed shoulders on the cutter links 25, some of theseshoulders being shown in contact with the edge 22 of plate 11 and edge23 of plate 12 in Fig. 1.

Thus the chain is slidably 'supported against inward displacement by theouter plates 11 and 12 and guided against lateral displacement by thesame plates, which is the conventional function of the bar groove.

However, the disk 15 and the rotatable ring 16 are so located that whenthe innermost edge 26 of each of the drive links approaches the outerend of the guide bar these link edges will contact the rotatable ring 16and lift the aforementioned bearing surfaces of the chain away from theplates 11 and 12, as indicated in Fig. l and Fig. 2. Thus, as the chainpasses around the outer end of the guide bar it becomes guided onlyagainst lateral displacement by the plates 11 and 12 but otherwise rideson the ring 16. In view of the anti-friction bearing elements 17 itspassage around the end of the bar is accomplished with a very muchreduced friction which reduces the power load and reduces the wear onthe end of the guide bar plates 11 and 12. The inner leg portions 21 ofthe guide links extend far enough between the guide plates so that therecan be no lateral displacement of the chain, if it is conventionallytight enough.

In assembling this device, the plate 13 may be laid upon the plate 11,for example, in the position shown and lightly tacked thereto by a fewspot welds. The disk 15 may then be located accurately in the positionshown and likewise spot welded to the plate 11. Thereafter the ring 16may be positioned about the disk and the bearing elements inserted inthe narrow groove surrounding the disk. The next step is to place theother outside plate 12 to overlie this assembly and then preferably weldor braze all three plates together at close intervals to make a ruggedlaminated assembly of the three plates, with the disk 15 secured to bothof them but with the ring 16 free to rotate therebetween.

outer-'ends Wear very rapidly-inithat area'.A My invention Y willinsurev a longer useful life toa chain bar, `lay-reducing friction andyet without.. weakening-1 the: bar;` assembly. Prior attemptsA to solvethisfproblem. have beenxunsatis-` factory for variousyreasons;

The drawing shows one preferred embodiment ofthe Y invention. However,it shouldxbeunderstood that the invention comprehends some`r11odif1ca-ti'on,from:V thefil-v lustrated embodimentv Withoutdepartingiromthscope 0fthe invention defined in the. appended claim.;

YHaving; shown and described my invention', I, claims,

Incombination with an endlesssawchainhaving center y links, opposedpairs of outer'horizontally extendingvlinks connecting the vcenterlinks,. cuttingf teethV on some; ofsaid i links,` the center linkshaving guide portionsV extendinginwardly of the inner marginsof:saicl=n'conneeting,linksV a predetermined distance, a guide nharassembly. comprisingv a pair of outer plates and ank intermediate` plateof lesser width and length secured-to and .betweentheouterpla't'esethereby providinga narroweperipheral Ygroove between opposedmarginal surfaces of the outer plates-tov receive and guide said guideVportions throughout the' entire course of travel of the chain alongboth longitudinal portions of the guide bar'as well as aroundtl'lerfreeendA ofthe bar, the peripheral edges of said outer'.platessbei'ng.v

spaced outwardly from the longitudinall marginsr ofthe intermediateplate along therlongitudinal portions of the guide bar a greaterdistance than said predetermined distance whereby the said peripheraledges of the outer plates constitute glide bearing surfaces for theinner margins of theconnecting links and simultaneously holdV said guideportions of the'center links out of contact with said intermediateplate, Vanfinner circular lrace member xed between and secured to saidouter plates adjoining the; free endxof; the Ybar beyond'. theradjacent'end of thel intermediate plate, avrotatable ring surrounding said racemember and` anti-friction elements between the ringand race member, asubstantial portion of the periphery of the ring at the free; end ofvvthe bar beingfembraced by the marginal portions of the outer plates, thedistance between the periphery of said portion of the ring and theadjacent peripheral margins of the outer plates being less than saidSpredeterminedf distance wherebyV the ringen-' gages the guide portionsofthe center links atrtheI free'V endof the bar and simultaneouslyholdsthe connecting` links'A out of-contact-withftheperipheral edgesof-theouter:

plateslat thezfree endoftheban v L Y V`References Cited inthe iile ofthis patent-

